The victim, identified as Mr Norbert Alfons de Wilde of Belgium, had reportedly been out to eat at a restaurant in Karon with a Thai companion, named as Ms Somporn Imprasong.
Ms Somporn told officers that at around 6.30pm, Mr Norbert complained of chest pains and excused himself from dinner to return, by himself, to his room at the Baan Karon Hotel so that he could take medication for a heart condition.
Ms Somporn said she returned to the room about 15 minutes later and found Mr Norbert lying down "uncomfortably" and who appeared to have breathing problems, prompting her to alert hotel staff who called for an ambulence.
Police searched the man's hotel room and did not report anything unusual.
Doctors at Patong Hospital were unable to revive the man, pronouncing him dead at 8.26pm, and subsequently confirmed that the cause of death was most likely a heart attack.